A combination needle of this type is known from, e.g., DE 35 08 013 C2. It is used for anesthesia and analgesia of the arm, block of the branchial plexus in the axillary region being preferably performed.
The prior-art combination needle is characterized by special designs of the pricking tip of the steel mandrel comprising a solid bar, which designs are suitable for piercing the nerve sheath consisting of solid tissue, also called neurilemma or fascia, by applying the smallest possible amount of force, and in which the risk of damage to the nerves is reduced to a minimum.
In addition, the particular position of the tip of the needle shall be able to be exactly localized. While the first requirements can be met by the shape of the pricking tip of the steel mandrel alone, the localization of the pricking tip at the nerve tract is performed by electrostimulation, which is carried out by applying an electric voltage of a certain intensity and of short duration. A plug socket is provided for this purpose at the end of the steel mandrel provided with the handle in the prior-art combination needle. Even though an anesthetist can read based on the length scale provided on the jacket surface of the plastic cannula how deep the cannula has penetrated into the skin, the anesthetist cannot determine from this how far the tip of the cannula is located in the vasomotor nerve sheath, because the distance between the vasomotor sheath and the skin surface or the pricking site differs from one patient to the next.
However, this plug socket has only a single-pole design, i.e., only one pole can be connected to a power source at the steel mandrel. The second necessary pole is connected to an electrode, which is placed somewhere outside on the body of the patient in question during the use of this prior-art combination needle. As such, there is a relatively great distance in all cases between the tip of the steel mandrel, which forms one electrode, and the second electrode, which is fastened at a favorable point outside on the patient's body.
From this arises the drawback that larger parts of the body are always affected by the electric effect of the electrostimulation. In patients who are provided with implanted electric devices, e.g., a cardiac pacemaker, this may lead to harmful results, which should be avoided by all means.